RF DEVICE WITH A COMMUNICATION MISMATCH SELF-CALIBRATION

Abstract

In a radiofrequency (RF) system with multiple transceivers configured to operate together (e.g., in beamforming applications), phase, delay, gain, or other offsets between individual transceivers can be compensated by pairwise measurements of RF signals transmitted by one active transmitter at a time as received by the receiver of the active transceiver and the receiver of another transceiver.

Claims

1-15. (canceled)

16. A radio frequency (RF) device, comprising: a first portion, comprising: a first antenna, a first transmitter, coupled to the first antenna, and configured to transmit a first RF signal, a first receiver, coupled to the first antenna, and configured to receive the first RF signal and a second RF signal; a second portion, comprising: a second antenna, a second transmitter, coupled to the second antenna, and configured to transmit the second RF signal, a second receiver, coupled to the second antenna, and configured to receive the first RF signal and the second RF signal; and control circuitry coupled to the first portion and the second portion, the control circuitry configured to: determine a variation between the first transmitter and the second transmitter or between first receiver and the second receiver, using the first RF signal received at the first receiver and the second receiver and the second RF signal received at the first receiver and the second receiver.

17. The RF device according to claim 16, wherein the control circuitry is further configured to compensate for the variation based on the determined variation.

18. The RF device according to claim 16, wherein the variation comprises: a delay variation, a phase variation, or a gain variation.

19. The RF device according to claim 16, further comprising: a first local oscillator associated with the first transmitter; and a second local oscillator associated with the second transmitter; wherein the control circuitry is further configured to: determine a local oscillator variation based on the determined variation, and compensate for the local oscillator variation.

20. The RF device according to claim 16, wherein the first portion and the second portion are formed as an array on the RF device.

21. The RF device according to claim 16, wherein the first transmitter is turned off when the second transmitter transmits the second RF signal and the second transmitter is turned off when the first transmitter transmits the first RF signal.

22. The RF device according to claim 16, wherein the first transmitter and the second transmitter transmit simultaneously.

23. The RF device according to claim 16, wherein the control circuitry is configured to: determine a first variation information (1) based on the first RF signal received at the first receiver; determine a second variation information (2) based on the first RF signal received at the second receiver; determine a third variation information (3) based on the second RF signal received at the first receiver; and determine a fourth variation information (4) based on the second RF signal received at the second receiver.

24. The RF device according to claim 23, wherein the control circuitry is further configured to: determine a first difference between the second variation information (2) and the third variation information (3); and determine a second difference between the first variation information (1) and the fourth variation information (4).

25. The RF device according to claim 16, wherein the control circuitry is further configured to combine determined variation information (1-4) to determine the variation.

26. The RF device according to claim 16, wherein the control circuitry is further configured to combine the first difference and the second difference to determine the variation.

27. The RF device according to claim 25, wherein the combination of the variation information cancels a self-interference, a transmitter variation, or a receiver variation.

28. The RF device according to claim 16, wherein the determination of the variation with respect to a transmitter variation is free of a receiver calibration.

29. The RF device according to claim 16, wherein the determination of the variation with respect to a receiver variation is free of a transmitter calibration.

30. The RF device according to claim 16, wherein the RF device is an ultra-wide band (UWB) device.

31. The RF device according to claim 16, wherein the RF device is a radar device.

32. The RF device according to claim 16, wherein the RF device is configured to perform a beam steering using the first transmitter and the second transmitter.

33. A method for operating a radio frequency (RF) device, wherein a first transmitter and a first receiver are coupled to a first antenna, and wherein a second transmitter and a second receiver are coupled to a second antenna, the method comprising: transmitting a first RF signal by the first transmitter; transmitting a second RF signal by the second transmitter; receiving the first RF signal and the second RF signal at the first receiver; receiving the first RF signal and the second RF signal at the second receiver; determining a variation between the first transmitter and the second transmitter, or a variation between the first receiver and the second receiver, using the first RF signal received at the first receiver and the second receiver, and the second RF signal received at the first receiver and the second receiver; and compensating for the variation based on the determined variation.

34. The method according to claim 33, further comprising: combining determined variation information (1-4) to determine the variation.

35. The method of claim 33, A method of forming a beam with a radio frequency (RF) device, the method comprising performing beamforming using the first transmitter and the second transmitter after compensating for the determined variation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] FIG. 1 illustrates a radio frequency device with two portions, according to an exemplary embodiment of the disclosure.

[0078] FIG. 2a illustrates a first step of determining variation information with a first transmitter transmitting, according to an exemplary embodiment of the disclosure.

[0079] FIG. 2b illustrates a second step of determining variation information with a second transmitter transmitting, according to an exemplary embodiment of the disclosure.

[0080] FIG. 3 illustrates an RF device for beam forming, according to an exemplary embodiment of the disclosure.

[0081] FIG. 4 illustrates a conventional local oscillator phase uncertainty.

[0082] FIG. 5 illustrates a conventional local oscillator phase drift.

DETAILED DESCRIPTION OF THE DRAWINGS

[0083] Before referring to the drawings, embodiments will be described in further detail, some basic considerations will be summarized based on which embodiments of the disclosure have been developed.

[0084] FIG. 1 shows a radio frequency device 100 (dual radar set-up), according to an exemplary embodiment of the disclosure. The device 100 comprises a first portion 110 with a first antenna 113 coupled to a first transmitter 111 (configured to transmit a first RF signal via the first antenna 113) and a first receiver 112 (configured to receive the first RF signal and a second RF signal via the first antenna 113), i.e. the first transmitter 111 and the first receiver 112 are collocated. The device 100 comprises a second portion 120 with a second antenna 123 coupled to a second transmitter 121 (configured to transmit the second RF signal via the second antenna 123) and a second receiver 122 (configured to receive the second RF signal and the first RF signal via the second antenna 123), i.e. the second transmitter 121 and the second receiver 122 are collocated. The first portion 110 and the second portion 120 are formed on the device 100 for example in form (or as part of) an (antenna) array.

[0085] FIG. 1 further illustrates the involved delays: [0086] delays from transmitter TX1, TX2 to antenna: .sub.TX1, .sub.TX2; [0087] delays from antenna to receiver RX1, RX2: TRX1, TRX2, self-interference delay: T.sub.SI. Self-interference (SI, also called spill-over, cross-coupling, cross-talk, own TX etc.) is caused by the coupling between transmitter and receiver.

[0088] The RF device 100 can now transmit: [0089] the first RF signal by the first transmitter 111 to the first receiver 112 (.sub.TX1, .sub.RX1); [0090] the first RF signal by the first transmitter 111 to the second receiver 122 (.sub.TX1, .sub.RX2, .sub.SI); [0091] the second RF signal by the second transmitter 121 to the first receiver 112 (.sub.TX2, .sub.RX1, .sub.SI); and [0092] the second RF signal by the second transmitter 121 to the second receiver 122 (.sub.TX2, .sub.RX2). Based on variation information obtained by these measurements, a variation (e.g. phase mismatch) can be determined (for example as described in detail for FIGS. 2a and 2b below), between the first transmitter 111 and the second transmitter 121 and/or between the first receiver 112 and the second receiver 122. Based on the determined variation, a suitable compensation scheme (e.g. introducing a delay) may be applied.

[0093] FIG. 2a illustrates a first step of determining a variation information with a first transmitter 111 transmitting, according to an exemplary embodiment of the disclosure.

[0094] The first transmitter 111 TX1 is turned on whereas the second transmitter 121 TX2 is turned off.

[0095] The first receiver 112 RX1 receives the first RF signal from TX1 and estimates a first phase (first variation information): .sub.1=(.sub.TX1+.sub.RX1).

[0096] The second receiver 122 RX2 receives the first RF signal from TX1 (over the air, via the antennas 113, 123) and estimates a second phase (second variation information): .sub.2=(.sub.TX1+.sub.SI+.sub.RX2).

[0097] FIG. 2b illustrates a second step of determining a variation information with a second transmitter 121 transmitting, according to an exemplary embodiment of the disclosure.

[0098] The second transmitter 121 TX2 is turned on whereas the first transmitter 111 TX1 is turned off.

[0099] The first receiver RX1 receives the second RF signal from TX2 (over the air via both antennas 113, 123) and estimates a third phase (third variation information): .sub.3=(.sub.TX2+.sub.SI+.sub.RX1).

[0100] The second receiver RX2 receives the second RF signal TX2 and estimates a fourth phase (fourth variation information): .sub.4=(.sub.TX2+.sub.RX2).

[0101] Based on the determined first to fourth variation information (illustrated as channel impulse response (CIR) in FIGS. 2a and 2b), a first (phase) difference and a second (phase) difference can be calculated:

[00001]$\begin{array}{c}\begin{array}{c}{}_2-{}_3=\left(T_{\mathrm{TX}1}+T_{\mathrm{SI}}+T_{\mathrm{RX}2}\right)-\left(T_{\mathrm{TX}2}+T_{\mathrm{SI}}+T_{\mathrm{RX}1}\right)\\ =\left(T_{\mathrm{TX}1}-T_{\mathrm{TX}2}\right)-\left(T_{\mathrm{TX}1}+T_{\mathrm{RX}2}\right)\end{array}\\ \begin{array}{c}{}_1-{}_4=\left(T_{\mathrm{TX}1}+T_{\mathrm{RX}1}\right)-\left(T_{\mathrm{TX}2}+T_{\mathrm{RX}2}\right)\\ =\left(T_{\mathrm{TX}1}-T_{\mathrm{TX}2}\right)+\left(T_{\mathrm{TX}1}+T_{\mathrm{RX}2}\right)\end{array}\end{array}$

[0102] Hereby, the following should be noted: [0103] the SI delay is completely cancelled, due to the symmetry of the measurements; [0104] the computed phase differences contain: [0105] the transmitter TX phase difference (.sub.TX1.sub.TX2) with the same sign, and [0106] the receiver RX phase difference (.sub.RX1.sub.RX2) with the opposite sign.

[0107] Using the determined variation information, in particular the determined differences, a transmitter variation (here phase difference) can be computed (adding (and scaling) the computed phase differences):

[00002]$1/2\left(\left({}_2-{}_3\right)+\left({}_1-{}_4\right)\right)=\left(T_{\mathrm{TX}1}-T_{\mathrm{TX}2}\right).$

[0108] Hereby, it should be noted that: [0109] the RX phase difference is completely cancelled, due to the (above mentioned) same/opposite sign behavior; [0110] the result is the desired TX phase difference (.sub.TX1.sub.TX2), indicative of the transmitter local oscillator phase misalignment.

[0111] In another application, receiver (RX) beam forming may be implemented to determine the angle (or direction) of arrival of an RF signal/wave, e.g. impinging on an antenna array. For example, the RF signal may be a radar reflection from a target (e.g. a person), and the output signals of multiple RXs connected to the array are combined such that the angle of the target relative to the array can be determined. In one implementation, the beam forming architecture comprises four receivers which are on the same chip or on different chips, for example comparable to the transmitters of FIG. 3. These receivers may be the same co-located receivers used for the calibration in the transmitter (beamforming) case.

[0112] If the delays through the multiple receivers differ, however, the angle of arrival determination may be inaccurate, leading to an inaccurate directional information of the target (e.g. the target may be determined to be at 30 deg instead of 20 deg).

[0113] To determine a receiver variation such as the phase (or delay) difference between two receiver local oscillators, the same method as described for the transmitter variation can be applied, comprising the same four variation information (phase) measurements, but combining them in a different manner as illustrated in the following:

((.sub.1.sub.4)(.sub.2.sub.3))=(.sub.RX1.sub.RX2).

[0114] As expected based on the considerations above, the self-interference and the transmitter variations is cancelled out.

[0115] In a final step, the determined variation (transmitter and/or receiver) can be compensated. For example, the transmitter local oscillator phases can be aligned based on the computed transmitter phase difference. In one example, the LO phase of either TX1 or TX2 is shifted relative to the other; e.g. by adding or subtracting an additional delay in the LO circuitry. Thereby, an efficient and reliable calibration may be enabled.

REFERENCE SIGNS

[0116] 100 RF device [0117] 105 Common reference clock [0118] 110 First portion [0119] 111 First transmitter [0120] 112 First receiver [0121] 113 First antenna [0122] 115 First local oscillator [0123] 120 Second portion [0124] 121 Second transmitter [0125] 122 Second receiver [0126] 123 Second antenna [0127] 125 Second local oscillator [0128] 150 Radar beam